Spherical carbon nanostructure and method for producing spherical carbon nanostructures

ABSTRACT

A method for producing carbon nanostructures according to the invention includes injecting acetylene gas into a reactant liquid. The injected acetylene molecules are then maintained in contact with the reactant liquid for a period of time sufficient to break the carbon-hydrogen bonds in at least some of the acetylene molecules, and place the liberated carbon ions in an excited state. The liberated carbon ions in the excited state then traverse a surface of the reactant liquid and enter a collection area where carbon ions combine to produce carbon nanostructures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/430,743, filed May 9, 2006, and entitled “Spherical CarbonNanostructure and Method for Producing Spherical Carbon Nanostructures,”now U.S. Pat. No. 7,922,993, which is a continuation-in-part of U.S.patent application Ser. No. 10/887,695, filed Jul. 9, 2004, and entitled“Method and Apparatus for Producing Carbon Nanostructures,” now U.S.Pat. No. 7,550,128 B2, and is a continuation-in-part of U.S. patentapplication Ser. No. 11/173,419, filed Jul. 1, 2005, and entitled“Reactant Liquid System for Facilitating the Production of CarbonNanostructures,” now abandoned. The Applicant claims the benefit of eachof these applications under 35 U.S.C. §120. The entire content of eachof these applications is incorporated herein by this reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to methods for manufacturing carbonnanostructures having a highly ordered spherical form. In particular,the invention relates to methods for placing carbon atoms in conditionto form impurity-free, spherical carbon nanostructures. The inventionalso includes a particular spherical carbon nanostructure.

BACKGROUND OF THE INVENTION

Carbon nanostructures have received a great deal of interest since theirdiscovery. It has been suggested that carbon nanostructures may haveimportant applications in electronics, in materials sciences, and in anumber of additional fields. As used in this disclosure, a “carbonnanostructure” comprises a structure made up of chemically bonded carbonatoms, with or without impurities or intentionally added materialsincorporated in the carbon structure or adjacent to the carbonstructure. Carbon nanostructures include structures in which carbonatoms are arranged in generally a series of interconnected carbon arraysformed into a tube, cylinder, sphere, crystal, sheet or other structure.Carbon nanostructures may be single walled or multiple walled nanotubes,nanofibers, nanorope, spheres, crystals, or nanowire. Single wallnanotubes include a single layer of the hexagonally arranged carbonatoms, while multiple walled nanotubes are made up of an inner layer ofcarbon atoms and a series of one or more outer layers of hexagonallyarranged carbon atom structures.

Despite the interest in carbon nanostructures and the potentiallyimportant uses for such structures, the practical application of carbonnanostructures in products has been slowed by the difficulty inmanufacturing such structures. Two general types of processes have beenemployed to produce or isolate carbon nanostructures. One process typeuses a plasma arc between carbon electrodes. U.S. Pat. Nos. 5,482,601and 5,753,088 describe such carbon plasma arc processes for producingcarbon nanotubes. Another process type involves simply isolatingnaturally formed carbon nanotubes from graphite and soot. Such anisolation process for carbon nanotubes is described in U.S. Pat. No.5,560,898.

The paper “Monodisperse Carbon Nanopearls in a Foam-Like Arrangement: aNew Carbon Nano-Compound for Cold Cathodes” by A. Levesque et al.discloses a process for manufacturing generally spherical carbonnanostructures having a diameter of approximately 150 nm. The processemployed chemical vapor deposition using nickel nano-cluster-catalyzeddissociation of acetylene at 700° C. As reported in this paper, when theprocess was performed at 600° C., only carbon nanotubes were producedrather than spherical carbon nanostructures.

The prior processes for producing or isolating carbon nanostructureshave been found to produce only small quantities of carbonnanostructures and/or produce carbon nanostructures of inconsistentquality. The low quality carbon nanostructures produced or isolated bythe prior methods commonly included metal or other atoms incorporated inthe carbon structure. These impurities incorporated in the walls of thecarbon nanostructures may have a negative impact on the qualities andproperties of the nanostructure and may render it unsuitable for anintended purpose. In particular, prior carbon nanostructure productiontechniques include no mechanism for preventing non-carbon atoms that maybe present in a carbon-bearing feed material from being incorporatedinto the carbon nanostructure. Also, prior carbon nanostructureproduction techniques tend to allow carbon from the feed material tobecome incorporated into the carbon nanostructures in an unpredictablefashion outside of the desired interconnected carbon array structure.This inclusion of amorphous carbon in the resulting carbon nanostructuregreatly degrades the properties and usefulness of the resulting carbonnanostructure.

SUMMARY OF THE INVENTION

The present invention provides methods for placing carbon in conditionto form substantially impurity-free carbon nanostructures. The presentinvention also encompasses a novel spherical carbon nanostructure.

A preferred method for producing carbon nanostructures according to theinvention includes injecting acetylene gas into a reactant liquid. Theinjected acetylene molecules are then maintained in contact with thereactant liquid for a period of time sufficient to break thecarbon-hydrogen bonds in at least some of the acetylene molecules, andplace the liberated, triple-bonded carbon C2 ions (which may also bereferred to as “acetylide” ions) in an excited state. This preferredmethod further includes enabling the liberated carbon C2 ions in theexcited state to traverse a surface of the reactant liquid and enter acollection area. Collection surfaces are provided in the collection areato collect carbon nanostructures.

As used in this disclosure and the accompanying claims an “excitedstate” will refer to the valence state for the particular material. Forexample, the heat from the preferred 1650° F. aluminum reactant liquidsupplies the required energy to change graphite, that is ground statecarbon, from atomic carbon into the divalent 3P energy state (requiring10.19 EV per atom), then to the 5S energy state (requiring another 1.88EV per atom), and finally to the SP3 hybrid state, or valence state(requiring another 8 EV per atom). The “excited state” for the C2acetylide ions thought to be produced according to the present inventionalso refers to the valence state of the C2 acetylide carbon ions.

The designation “carbon ion” will be used in this disclosure and theaccompanying claims to refer to any single carbon atom or any group ofbonded carbon atoms that have a net charge due to reaction between acarbon-bearing feedstock material with the reactant liquid. Theacetylene feedstock described above reacts with the reactant liquid toproduce a carbon ion made up of a pair of triple-bonded carbon atoms(thus referred to as an acetylide ion). Feedstock materials containing asingle pair of double-bonded carbon atoms, for example, may react with areactant liquid according to the present invention to produce a carbonion made up of a pair of double-bonded carbon atoms, which may bereferred to as an ethyleneide ion. It will be noted that both of thetriple-bonded carbon ion and the double-bonded carbon ion are C2 ions.

The process of reacting the acetylene with the reactant liquid accordingto the invention also liberates hydrogen atoms from the acetylenemolecules. This liberated hydrogen may be vented from the collectionarea. Some forms of the invention also inject an inert gas into thereactant liquid together with the acetylene. This inert gas is alsopreferably vented from the collection area.

The method may further include adding heat to the collection area with aheater element. For example, one or more heater elements such aselectrical resistance heater elements may be included in the collectionarea, and operated to heat both the collection area and the collectionsurfaces provided in the collection area.

One preferred carbon nanostructure production process employssubstantially pure liquid aluminum (99% aluminum by mass composition) atapproximately 1650° F. as the reactant liquid. This reactant liquid hasbeen found to liberate the desired carbon ions, and place these ions inthe desired excited energy state for the production of carbonnanostructures. The process of producing carbon nanostructures mayinclude heating the collection surfaces to between approximately 1350°F. and 1620° F. The process may also be performed without applying anyheat to the collection surfaces other than heat from the reactant liquidand any heat released from the formation of carbon nanostructures. Forexample, the process of producing spherical carbon nanostructures may beperformed with the temperature of the collection surfaces ranging fromapproximately 100° F. to 590° F. All of the spherical carbonnanostructures produced by the above-described preferred process havebeen produced without any nickel catalyst or other catalyst deposited onthe collection surfaces. It should be noted that the nanospheresproduced using the liquid aluminum reactant liquid are thought to benucleated by metal vapors located just above the surface of the reactantliquid. It is believed that the nanospheres form or begin to form as thehigh energy excited C2 triple-bonded carbon ions traverse the surface ofthe reactant liquid and mingle with the metal vapors just above thesurface of the reactant liquid.

Based on an analysis of the acetylene feedstock material used inprocesses according to the present invention and of the energy availablein the preferred aluminum reactant liquid, it is believed that thespherical carbon nanostructures collected from the above-describedprocesses are composed of one or more chains of carbon atoms arrangedwith alternating triple and single bonds between adjacent carbon atomsin each chain. In particular, it is believed that the reactant liquidsupplies the required energy to break the carbon-hydrogen bonds in theacetylene molecules and place the resulting acetylide carbon C2 ions inthe high energy, valence state, but leaves the triple carbon bondintact. These valence state acetylide carbon C2 ions are believed tothen combine using the remaining bond site for each carbon atom in thetriple-bonded carbon C2 ion to make the alternating triple and singlebond structure of carbon atoms.

These and other advantages and features of the invention will beapparent from the following description of the preferred embodiments,considered along with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of an apparatus that has beenemployed to produce spherical carbon nanostructures according to thepresent invention.

FIG. 2 is a diagrammatic representation of an apparatus embodying theprinciples of the invention showing the relationship between thereactant liquid bath, collection chamber, loading chamber, andcollection structure when the apparatus is being prepared to receive thecollection structure in position to collect carbon nanostructures.

FIG. 3 is a diagrammatic representation similar to FIG. 2, but showingthe condition of the apparatus when it is producing and collectingcarbon nanostructures.

FIG. 4 is a process flow chart showing a process for producing sphericalcarbon nanostructures according to one preferred form of the presentinvention.

FIG. 5 is an isometric view of a rack used in one preferred collectionstructure according to the present invention.

FIG. 6 is a view in section taken along line 6-6 in FIG. 5, and showingcollection plates loaded into the rack in phantom lines.

FIG. 7 is a transmission electron microscope image of a sample ofmaterial collected in Example 1.

FIG. 8 is a transmission electron microscope image of a sample ofmaterial collected in Example 1, but at a higher level of magnificationas compared to the image shown in FIG. 7.

FIG. 9 is a scanning electron microscope image of a sample of materialcollected in Example 1.

FIG. 10 is another scanning electron microscope image of a sample ofmaterial collected in Example 1 including dimension markings for some ofthe spherical structures.

FIG. 11 is a scanning electron microscope image of a sample of materialcollected in Example 2.

FIG. 12 is another scanning electron microscope image of a sample ofmaterial collected in Example 2.

FIG. 13 is another scanning electron microscope image of a sample ofmaterial collected in Example 2 including dimension markings for some ofthe spherical structures.

DESCRIPTION OF PREFERRED EMBODIMENTS

The claims at the end of this application set out novel features whichthe Applicant believes are characteristic of the invention. The variousadvantages and features of the invention together with preferred modesof use of the invention will best be understood by reference to thefollowing description of illustrative embodiments read in conjunctionwith the drawings introduced above.

Referring to the diagrammatic representation of FIG. 1, an apparatus 100for producing carbon nanostructures according to the present inventionincludes a number of components that can be separated generally intothree interrelated systems, a heating system shown in dashed box 101, ananostructure production and collection system (“production system”)shown in dashed box 102, and an injection system shown generally atreference numeral 103. A reactant liquid, the surface level of which isshown at 105 in FIG. 1, is heated in heating system 101 and circulatedbetween that system and a reaction chamber 106 of production system 102.Injection system 103 allows a stream of feedstock material and/or purgegas to be injected into reaction chamber 106 at a point below the level105 of reactant liquid in the reaction chamber. In addition to reactionchamber 106, production system 102 further includes a collection chamber108 and a loading chamber 109.

In the operation of apparatus 100, the carbon-bearing feedstock materialinjected into reaction chamber 106 below the surface level 105 of thereactant liquid in the reaction chamber, reacts quickly with thereactant liquid to produce chemically excited carbon ions containingone, two, or more carbon atoms, depending upon the nature of thefeedstock. The chemically excited carbon ions together with materialssuch as hydrogen released from the feedstock molecules and together withany purge gas atoms traverse the surface 105 of the reactant liquid inreaction chamber 106 and flow up into collection chamber 108. Above thereactant liquid and in collection chamber 108, the carbon ionschemically combine with other carbon ions to form carbon nanostructuresand collect on removable collection surfaces in the collection chamber.

These collection surfaces will be shown and described further below inconnection with FIGS. 2, 3, 5 and 6. Other atoms such as hydrogen atomsand purge gas atoms, eventually escape through a pressure relief valve110 associated with loading chamber 109. After a desired collectionperiod, the collection surfaces (not shown in FIG. 1) are removed fromcollection chamber 108 and cooled in loading chamber 109. Ultimately,the collection surfaces are removed from loading chamber 109, and thecarbon nanostructures that have collected on the collection surfaces areremoved from those surfaces. Further details of the operation ofapparatus 100 will be described below in connection with FIGS. 2-6.

Reaction chamber 106 comprises a vessel suitable for containing a bathof a desired reactant liquid. The particular reactant liquid used in theexamples described below comprises substantially pure liquid aluminum(99% aluminum by mass composition) at a temperature of approximately1650° F. (between about 1642° and 1655° F.), and the vessel included inreaction chamber 106 is lined with a suitable refractory material whichwill not react with the liquid aluminum. Heating system 101 supplies theheat necessary to at least keep the reactant liquid at the desiredtemperature necessary to produce the desired reaction with the feedstockand chemically excite the resulting carbon ions to the desired valencelevel. Thus, heating system 101 also includes a vessel 111 adapted tocontain the reactant liquid and apply heat to the liquid to maintain thedesired temperature in the liquid. A circulation device 112 is alsopreferably associated with heating system 101 and/or reaction chamber106 to provide the desired circulation between the vessel included inthe reaction chamber and the vessel associated with the heating system101. In the preferred arrangement shown in FIG. 1, the heating systemvessel 111 and the vessel making up reaction chamber 106 compriseessentially a single vessel separated by a baffle 114 that forms abarrier between a heating area 115 associated with heating system 101and an area 116 above the reactant liquid level 105 in reaction chamber106. The heating system 101 shown in FIG. 1 includes burners 118 forburning a suitable fuel to heat the material on the heating system sideof baffle 114. The circulation device 112 shown in FIG. 1 includes astirring element 120 which is driven by a motor 121 to provide thedesired circulation under baffle 114.

The invention is not limited to the particular arrangement of heatingsystem 101 and reaction chamber 106 shown in FIG. 1. For example, ratherthan heating the reactant liquid with combustible fuels as shown in FIG.1, electrical induction heating or any other suitable heatingarrangement or combination may be used to hold the reactant liquid atthe desired temperature. In any case, the initial heating of thereactant liquid may be accomplished in heating system (such as system101) or in a separate system (not shown) which feeds the pre-heatedreactant liquid into the heating system. Furthermore, processesaccording to the present invention may be performed in a system in whichthe reaction chamber includes a vessel separate from the vesselassociated with the heating system and in which a suitable connectionbetween the separate vessels allows the desired circulation of thereactant liquid between the vessels. Where electrical heatingarrangements are used to heat the reactant liquid, the heating may infact occur in at least a portion of the reaction chamber itself, andthus a separate heating vessel may not be required. The presentinvention encompasses any arrangement by which the desired reactantliquid may be held at the desired temperature for reacting the feedstockmaterial as will be described further below.

Injection system 103 includes a purge gas vessel 124 and a feedstockvessel 125 connected by suitable conduits 126 and 127, respectively, toan injection conduit 128. The flow of material through conduits 126 and127 is controlled by control valves 130 and 131, respectively. Injectionconduit 128 terminates at reaction chamber 106 so that materials fromthe vessels 124 and 125 may be injected into the liquid reactantmaterial in the reaction chamber. Purge gas vessel 124 preferablycontains a suitable inert purge gas such as argon which may becontinuously injected into the system to prevent the reactant liquidfrom flowing into injection conduit 128. The purge gas is also used topurge the system of air as will be discussed below in connection withFIGS. 2 and 3. Feedstock vessel 125 contains the material that is to bereacted with the reactant liquid in reaction chamber 106 to producechemically excited carbon ions which combine in the system to producethe desired carbon nanostructures. It will be appreciated that theinjection system 103 shown in FIG. 1 is shown only diagrammatically andthat other valves and control devices may be included in the variousconduits to direct feedstock and/or purge gas into reaction chamber 106as desired according to the invention.

Further details regarding production system 102 may be described inconnection with FIGS. 2 and 3. In particular, FIGS. 2 and 3 show areaction tunnel structure 201 in reaction chamber 106, heater elements202 in collection chamber 108, and an insulating slide door 204 made ofsteel or other suitable material interposed between the collectionchamber and loading chamber 109. FIGS. 2 and 3 also show acollection/recovery arrangement shown generally at reference numeral206. Collection/recovery arrangement 206 includes a collection structure207 and an insulating plate 208 both connected to a manipulatingstructure 210.

Reaction tunnel structure 201 is included in the system to help increasethe contact time between the feedstock material and reactant liquid andthereby ensure the desired decomposition and chemical excitation of thefeedstock material. Reaction tunnel 201 also causes the input materialto rise through the reactant liquid generally in the center of reactionchamber 106. The purge gas and/or feedstock injected into reactionchamber 106 follows the path generally shown at arrow 212 in FIGS. 2 and3. Reaction tunnel 201 preferably comprises an inverted U-shapedstructure formed from a suitable refractory material or having arefractory material exterior to withstand contact with the reactantliquid in reaction chamber 106.

Heater elements 202 are included in collection chamber 108 to helpcontrol the temperature within the collection chamber and thetemperature of the collection structure as will be described furtherbelow. In one preferred arrangement, heater elements 202 compriseelectrical resistance heater elements that extend along one or moresides of collection chamber 108. Although not shown in FIGS. 2 and 3, itwill be appreciated that a suitable power supply supplies electricalpower to heater elements 202 as required to control the temperature inthe collection chamber 108 and collection structure 207.

Collection structure 207 is included in the production system 102 toprovide appropriate collection surfaces on which carbon nanostructuresmay collect according to the present invention. Further details of onepreferred collection structure will be described in connection withFIGS. 5 and 6. It will be noted by comparing FIGS. 2 and 3 thatcollection structure 207 may reside in two different positions in theoperation of production system 102. FIG. 2 shows collection structure207 in an uppermost position in which it is fully contained in loadingchamber 109. FIG. 3 shows collection structure 207 in its lowermostposition in which it is fully contained in collection chamber 108.Manipulating structure 210 is included in the collection/recoveryarrangements 206 to allow collection structure 207 to be positionedalternatively in the uppermost position shown in FIG. 2 and thelowermost position shown in FIG. 3. Insulating plate 208 is included incollection/recovery arrangements 206 to help insulate the loadingchamber 109 from the elevated temperatures in collection chamber 108when collection structure 207 is in its lowermost position shown in FIG.3. Any suitable material such as spun ceramic wool may be used forinsulating plate 208.

Processes according to the present invention may be described withreference to the process flow chart shown in FIG. 4 and with referenceto the example production system 102 shown in FIGS. 2 and 3. Referringfirst to FIG. 4, one preferred process according to the inventionincludes maintaining a reactant liquid in a desired reactant conditionas indicated at process block 401. This desired reactant condition isone in which the feedstock will react with the reactant liquid tochemically separate carbon atoms from other constituents in thefeedstock material and chemically excite the resulting carbon ions. Asshown at process block 403 in FIG. 4, the preferred process includesplacing a suitable carbon-bearing feedstock in contact with the reactantliquid in the desired reactant condition to produce and chemicallyexcite the carbon ions. These liberated carbon ions are then allowed totraverse a surface of the reactant liquid and enter a collection chamberas shown at process block 404. As indicated at process block 405 in FIG.4, carbon nanostructures are collected on collection surfaces in thecollection chamber. These collection surfaces may be provided asindicated at process block 402 in FIG. 4. The collected carbonnanostructures are ultimately removed from the collection surfaces asshown at process block 406.

Referring now to FIG. 2, manipulating arrangement 210 is initially heldin its uppermost position for each cycle of operation, with insulatingdoor 204 closed to help isolate loading chamber 109 from the heatassociated with the reactant liquid held in reaction chamber 106. Inthis position, the airlock door (not shown in the figures) associatedwith loading chamber 109 may be opened to insert collection structure207 on the receiving structure associated with manipulating arrangement210, so that the collection structure resides in the position shown inFIG. 2. One preferred receiving structure which allows the collectionstructure 207 to be removably positioned on manipulating structure 210will be described below in connection with FIGS. 5 and 6. Once theairlock door associated with loading chamber 109 is closed, the purgegas which is preferably continuously injected into reaction chamber 106through injection conduit 128 eventually displaces air that has enteredloading chamber 109 in the course of loading collection structure 207 tothe position shown in FIG. 2. It is noted that insulating door 204 doesnot provide a gas tight seal between collection chamber 108 and loadingchamber 109 when the insulating door 204 is closed, and thus the argongas preferably continuously injected through injection conduit 128, maycontinue to flow into loading chamber 109 even when the insulating dooris closed in the position shown in FIG. 2.

Once the air is purged from loading chamber 109, production system 102is ready to be placed in a condition to collect carbon nanostructures.It should be noted that during the time of the operation cycle that thecollection structure is either removed from production system 102 or inthe loaded initial position shown in FIG. 2, the reactant liquid held inreaction chamber 106 is preferably maintained in the desired reactantcondition. Maintenance of the reactant liquid in the desired conditionduring the injection of carbon-bearing feedstock as described belowcorresponds to the step shown at process block 401 in FIG. 4.

With the air purged from loading chamber 109, insulating door 204 may beopened and manipulating structure 210 lowered to position collectionstructure 207 in the position shown in FIG. 3. In this lowermostposition, shown in FIG. 3, the surfaces associated with collectionstructure 207 provide collection surfaces in collection chamber 108 onwhich carbon nanostructures may collect according to the invention. Thisprovision of collection surfaces occasioned by placing collectionstructure 207 in the position shown in FIG. 3 corresponds to the stepshown at 402 in FIG. 4. In this lowermost position, insulating plate 208fits loosely over the opening for insulating door 204. This loose fitover the opening for insulating door 204 allows purge gas and othergasses to flow up from collection chamber 108 into loading chamber 109and ultimately exit production system 102 as indicated by arrow 214.

Once production system 102 is in the position shown in FIG. 3, purge gasalone may still be injected into reaction chamber 106 for a period oftime to allow the collection structure 207 to reach a desired operatingtemperature for the production and collection of carbon nanostructuresaccording to the invention. Heater elements 202 may be operated to helpheat the contents of collection chamber 108, including collectionstructure 207. When the temperature of collection structure 207 and thetemperature in collection chamber 108 have reached the desired levels,feedstock or feedstock and purging gas may be injected into reactionchamber 106 as shown at arrow 212 in FIG. 3. According to the invention,carbon ions containing one, two, or more carbon atoms are liberated fromthe feedstock by reaction with the reactant liquid in reaction chamber106. This injection of feedstock and production of carbon ionscorresponds to the process step shown at block 403 in FIG. 4. Thesecarbon ions rise quickly through the reactant liquid and traverse thereactive liquid surface 105 to flow into collection chamber 108 inaccordance with the process step shown at block 404 in FIG. 4.Ultimately, the carbon ions bond together to produce the desired carbonnanostructures and collect on surfaces in collection chamber 108, andparticularly surfaces associated with collection structure 207. Thiscollection of carbon nanostructures corresponds to the process stepshown at block 405 in FIG. 4. It should be noted that materials releasedfrom the feedstock molecules, such as hydrogen in the case of anacetylene feedstock, are able to rise up through collection chamber 108,pass around plate 208 in the position shown in FIG. 3, together with theargon purge gas and eventually exit loading chamber 109. This venting asindicated by arrow 214 in FIG. 3 is preferably accomplished through thepressure relief valve 110 shown in FIG. 1.

After a desired collection period in which feedstock is injected intoreaction chamber 106 with production system 102 in the position shown inFIG. 3, the feedstock flow is terminated so that only purge gascontinues to flow into reaction chamber 106. Manipulating structure 210is then used to raise collection structure 207 up to the position shownin FIG. 2. At this point, insulating door 204 may be closed to theposition shown in FIG. 2 and collection structure 207 may be allowed tocool as necessary to allow the structure to be removed from loadingchamber 109. To remove the collection structure 207, the airlock door(not shown) associated with loading chamber 109 is opened and thecollection structure 207 is removed as facilitated by the connection tomanipulating arrangement 210. Collected carbon nanostructures on thesurfaces of collection structure 207 may then be brushed or scraped offonto a suitable surface and then moved to suitable containers. Thisremoval of carbon nanostructures corresponds to the process step shownat block 406 in FIG. 4. Collection structure 207 may then be readied foranother cycle of operation. In one preferred process, the surfaces ofcollection structure 207 are particle blasted to prepare the surfacesfor the next operation cycle.

FIGS. 5 and 6 show a rack 501 that may be used as a portion of thecollection structure 207 described in connection with FIGS. 2 and 3.This preferred rack 501 supports a number of collection plates whichprovide the primary collection surfaces for collecting carbonnanostructures according to the invention. In order to more clearly showthe rack structure, the isometric view of FIG. 5 shows only rack 501without the collection plates. However, the section view of FIG. 6 showsthe plates 502 and 503 in phantom lines as they would be received onrack 501.

Rack 501 includes four U-shaped members, two upwardly facing U-shapedmembers 506 with one at either end of the structure, and two downwardlyfacing U-shaped members 507 spaced apart in a center portion of therack. A series of rods 508 are connected to these U-shaped members 506and 507 with the rods spaced apart to providing a series of channels 509for receiving collection plates 502 shown in FIG. 6. The particular rack501 shown in FIGS. 5 and 6 includes seven rods 508 on each lateral sideof the collection structure producing six separate channels 509 whichmay each receive a collection plate 502. At the bottom of rack 501 arelocated a series of spaced apart inverted T-shaped structures 511 andangle members 512 which together form five slots 514 for receivingadditional collection plates 503. As indicated in FIG. 6, channels 509hold collection plates 502 in a horizontal orientation while the slots514 at the bottom of rack 501 support collection plates 503 in avertical orientation.

Rack 501 also includes an arrangement for enabling the rack to beremovably suspended from the manipulating structure 210 shown in FIGS. 2and 3. The illustrated connecting arrangement 516 includes two anglemembers 518 which are connected to the two downwardly opening U-shapedmembers 507 of rack 501. The outwardly facing upper portions 519 ofthese angle members 518 may be slidably received in a slot mounted atthe bottom of manipulating structure 210. FIG. 6 shows this receivingslot structure 522 in phantom lines. In this arrangement, rack 501 maybe loaded into the production system 102 shown in FIGS. 2 and 3 simplyby opening the airlock door (not shown) associated with loading chamber109 and inserting the outwardly extending portions 519 of angle members518 into the slot formed in slot structure 522 located at the bottom ofmanipulating structure 210. Conversely the collection structure 207 maybe removed simply by sliding the upper portions 519 of angle members 518off of the receiving slot structure 522 and pulling the collectionstructure through the open airlock door associated with loading chamber109 (but not shown in the figures).

Methods of producing carbon nanostructures according to the inventionand the particular carbon nanostructures produced by such methods may bedescribed further in connection with the following examples. Each ofthese examples used a test apparatus as described above in connectionwith FIGS. 1 through 3 and a collection structure rack as described inFIGS. 5 and 6. Thus, the various elements of the test apparatusdescribed below will retain the same references numbers used for thecorresponding elements of the structures shown in FIGS. 1 through 3, 5and 6. In the test apparatus used for these examples, collection chamber108 comprised a rectangular chamber having internal dimensions ofapproximately seventeen (17) inches high, fifteen (15) inches wide, andfifteen (15) inches deep. Three rows of heater elements 202 wereincluded against three walls of the collection chamber generally in theposition shown in FIGS. 2 and 3. Reaction chamber 106 in the testapparatus had internal dimensions of approximately twenty-five (25)inches high, fifteen (15) inches wide, and fifteen (15) inches deep.Substantially pure aluminum (99% aluminum by mass composition) at atemperature of approximately 1650° F. (1642° F. to 1655° F.) wasmaintained in the reaction chamber approximately eighteen (18) inchesdeep. The feedstock material and purge gas were injected into thereaction chamber at approximately seventeen (17) inches below thesurface of the liquid aluminum into a tunnel structure 201 as describedabove in FIGS. 2 and 3. The outlet end or lip of tunnel structure 201was positioned generally in the center of the reaction chamberapproximately sixteen (16) inches below the surface 105 of the liquidaluminum. In each of the examples, the collection plates 502 (and 503for Example 1 below) shown in FIG. 6 comprise plates of 304 stainlesssteel approximately three-sixteenths ( 3/16) of an inch thick. Each ofthe horizontally arranged plates 502 was ten and a half (10.5) incheswide, and eleven (11) inches deep, while the vertically oriented plates503 (used only in Example 1) were approximately five (5) inches high andeleven (11) inches deep. The rack 501 itself as shown in FIGS. 5 and 6was approximately sixteen (16) inches high, thirteen (13) inches wide,and thirteen (13) inches deep. This arrangement left a clearance ofapproximately 1 inch between rack 501 and the inner wall of collectionchamber 108. Other operating parameters for the test apparatus will bedescribed in connection with the respective example.

EXAMPLE 1

In one test of the apparatus described above, rack 501 was loaded withsix horizontal collection plates 502 spaced approximately one-half inchapart and five vertical collection plates 503 spaced approximately oneand one-half (1.5) inch apart. The collection structure 207 made up ofrack 501 and loaded collection plates 502 and 503 was then placed intoloading chamber 109 suspended on manipulating structure 210 as describedabove in connection with FIG. 6. The airlock door associated withloading chamber 109 was then closed and the continuously injected argongas allowed to purge the loading chamber of air that entered as theairlock door was open. After purging loading chamber 109 of air,insulating door 204 was opened and manipulating structure 210 was usedto lower collection structure 207 from the position shown in FIG. 2 tothe position shown in FIG. 3. In this lowered position, with collectionstructure 207 residing in collection chamber 108, the lowermost ends ofthe vertically oriented collection plates 503, resided approximately two(2) inches above the surface 105 of the liquid aluminum reactant liquid.From this point in the collection test, only argon was stillcontinuously injected into the reactant liquid and heater elements 202were operated to increase the temperature of the collection structure207 to approximately 1400° F. Once this collection surface temperaturewas reached, commercial grade acetylene (comprising approximately 48%acetylene and 52% acetone) at room temperature of approximately 70° F.was injected into the reactant liquid at a rate of approximately two (2)liters per minute along with the argon gas also at approximately two (2)liters per minute. This injection of argon gas and acetylene-acetonemixture was continued for a period of approximately two (2) hours untilapproximately 133 grams of carbon from the acetylene-acetone mixture hadbeen injected. The injection of the acetylene-acetone mixture was thenstopped leaving the continuous stream of argon gas at approximately two(2) liters per minute.

Once the injection of the acetylene-acetone mixture was stopped,manipulating structure 210 was used to raise collection structure 207 upinto the position shown in FIG. 2, with the collection structureresiding in loading chamber 109, and insulating door 204 was closed.Collection structure 207 was then allowed to cool to approximately 212°F. at which point the airlock door associated with loading chamber 109was opened, and the collection structure was removed to an aluminumfoil-covered table top. The vertical plates 503 were removed from rack501 prior to placing the rack on the foil-covered table. A shiny andpowdery appearing, black material was observed on the surfaces of all ofthe collection plates 502 and 503 and on the surfaces of rack 501itself. Plastic foam brushes were used to brush off the black materialonto the aluminum foil and then the black material was placed into glasssample containers. This test and black material recovery procedureyielded approximately sixty (60) or more grams of the black material.

The black material collected in these sample containers was laterexamined with a transmission electron microscope (TEM) and scanningelectron microscope (SEM). FIGS. 7 and 8 are TEM images of the collectedblack material. These images show that the black material collected asdescribed above is made up almost exclusively of spherical structures.The TEM image shown in FIG. 8 shows that the spherical structures arehighly ordered consistently across the surface of each sphere, and thatthe spheres appear to be composed of a series of concentric strings ofcarbon material. These concentric strings appear consistent throughout asignificant portion of the surface of the respective sphericalstructure, that is, throughout 50% or more of the respective spheresurface visible in FIG. 8. FIGS. 9 and 10 are SEM images of this samematerial collected as described above. These SEM images were taken fromthe same sample of the collected material which produced the TEM imagesof FIGS. 7 and 8. The SEM images confirm the uniform sphericalstructures making up the material. The spherical carbon nanostructuresincluded in the sample material were as small as approximately sixty-two(62) nanometers in diameter as shown in FIG. 10. Energy dispersivespectroscopy (EDS) at two locations in material from this sample havingthe structure shown in FIGS. 7 through 10 showed that the material wasmade up largely of carbon with only a small percentage of oxygen.Specifically, one EDS result indicated that the spherical material was94.37% carbon by mass composition, and 5.03% oxygen by mass composition.The second EDS result indicated the spherical material was 96.43% carbonmass composition and 3.57% oxygen by mass composition. It is believedthat the oxygen atoms indicated in the EDS results were not incorporatedin the spherical structures themselves, but were extraneous atomsincluded in among the spherical structures.

The collection process described above was performed seven times in oneseries of tests. The following table shows the temperatures measured inthe collection structure 207 at the start of the acetylene-acetonemixture injection and at the end of the acetylene-acetone mixtureinjection. TEM and SEM analyses of samples taken from all of these seventest operation cycles showed results similar to those shown in FIGS. 7through 10.

TABLE 1 Starting Ending Temperature (° F.) Temperature (° F.) 1394 15431378 1526 1375 1441 1521 1616 1415 1569 1370 1416 1527 1608

It should be noted that the reaction of the acetylene-acetone mixturewith the aluminum reactant liquid in this example is believed to producetwo different carbon ions, together with hydrogen and oxygen atomsreleased from the original feedstock molecules. It is believed that thereaction in the reactant liquid releases one triple-bonded C2 carbon ionand two hydrogen atoms from each acetylene molecule. It is believed thatthe reaction in the reactant liquid also releases two C1 (single carbonatom) carbon ions, one carbon-oxygen ion, and six hydrogen ions fromeach acetone molecule.

It should also be noted that tests similar to those set out in Example 1were conducted with various metal catalysts included on the collectionsurfaces. Iron, cobalt, and nickel catalysts were used in differenttests with the acetylene-acetone feedstock. In these tests, with thecollection surfaces starting at a temperature of around 1450° F., carbonnanofibers were collected on the collection surfaces rather than thecarbon nanospheres shown in FIGS. 7 through 10.

EXAMPLE 2

The same procedure described in Example 1 above was conducted in anadditional series of tests each using a lower initial temperature ofcollection structure 207 prior to starting the injection of theacetylene-acetone mixture, and using only horizontal collection plates502. In these collection procedures, once collection structure 207 wasin the position shown in FIG. 3, heater elements 202 were not activatedand the acetylene-acetone mixture was injected immediately, prior to anysignificant heating of the collection structure. In these tests, thestarting temperature of collection structure 207 was approximately 100°F., and the ending temperature was approximately 590° F. Also, for thesetests, the flow of acetylene-acetone mixture was increased to seven (7)liters per minute for the injection period of two (2) hours. FIGS. 11-13show SEM images of material collected from one of these tests. As shownin the SEM images, these tests also produced generally spherical carbonnanostructures with some as small as approximately seventy-one (71)nanometers in diameter. An EDS result for the spherical material fromthe same sample as the spherical material shown in FIGS. 11-13 indicatesthe material includes 99.29% carbon by mass composition and 00.71%oxygen by mass composition.

Although the particular TEM and SEM images in the figures show that thespherical nanostructures produced according to Example 1 and Example 2included spheres well less than 150 nanometers, it is believed thatthere was a general size difference in the carbon nanospheres producedin the two examples. Qualitatively, the carbon nanospheres producedaccording to Example 1 appeared to be larger on average than the carbonnanospheres produced according to Example 2.

This apparent size difference resulting from cooler collection surfacetemperatures in Example 2 suggests that it may be desirable to includesome structure in the system to further limit or control the temperatureof the collection surfaces during the course of carbon nanostructurecollection. One preferred arrangement for limiting or controlling thetemperature of the collection surfaces in a collection chamber such aschamber 108 in FIGS. 1-3, includes an arrangement for circulating atemperature controlling fluid through the structures making up thecollection surfaces in the system. For example, collection plates 502 or503 shown in FIG. 6 may include passageways in their interior forcirculating a temperature controlling fluid. The fluid may be used tocool the collection surfaces associated with the plates, or heat thecollection surfaces further. Such a temperature controlling system wouldfurther require a system for conditioning the temperature controllingfluid to the desired state and temperature before circulating the fluidthrough the plates, and also a suitable device such as a pump orcompressor for producing the desired circulation.

A further test similar to the test described in Example 2 was also runsubstituting substantially pure methane gas for the acetylene-acetonemixture. The methane gas at about 70° F. was injected at a rate of seven(7) liters per minute with the argon gas for a period of time to injectan equivalent amount of carbon into the test system (about 133 grams).This test produced a dull black, powdery material on the collectionplates and rack structure. However, this collected material was found toinclude no apparent carbon nanostructures. Rather, the collectedmaterial appeared from SEM scans to be substantially pure carbon eitheras separate atoms or in collections of atoms too small to be visible inthe SEM images.

As used herein, whether in the above description or the followingclaims, the terms “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” and the like are to be understood to beopen-ended, that is, to mean including but not limited to. Any use ofordinal terms such as “first,” “second,” “third,” etc., in the claims tomodify a claim element does not by itself connote any priority,precedence, or order of one claim element over another, or the temporalorder in which acts of a method are performed. Rather, unlessspecifically stated otherwise, such ordinal terms are used merely aslabels to distinguish one claim element having a certain name fromanother element having a same name (but for use of the ordinal term).

The above described preferred embodiments are intended to illustrate theprinciples of the invention, but not to limit the scope of theinvention. Various other embodiments and modifications to thesepreferred embodiments may be made by those skilled in the art withoutdeparting from the scope of the present invention. In particular, thepresent invention is not limited to the particular test apparatusdescribed above in connection with the figures and the examples. Rather,the above-described processes may be performed with substantially anyapparatus that (1) allows a carbon-bearing feedstock to be injected intoa volume of reactant liquid to facilitate the reaction of the feedstockwith the reactant liquid and desired chemical excitation of theresulting carbon ions, and that (2) provides a suitable collectionchamber and collection surface. For example, the apparatus shown in U.S.Pat. No. 6,227,126 may be used to provide the desired contact andreaction between the feedstock material and reactant liquid. The entirecontent of this prior patent is incorporated herein by this reference.Also, it will be appreciated that the present invention is not limitedto the substantially pure aluminum reactant liquid. Any other liquidthat provides the desired reactions with the carbon-bearing feedstockand chemical excitation of the resulting carbon ions may be used as areactant liquid according to the invention.

1. A method for producing carbon nanostructures, the method including:(a) maintaining a volume of reactant liquid having an energy levelsufficient to (i) liberate a respective carbon ion from a respectiveacetylene molecule in a stream of acetylene molecules placed in thevolume of reactant liquid, and to (ii) place the respective liberatedcarbon ion in an excited state; (b) maintaining a collection areaimmediately above a surface of the volume of reactant liquid; (c)injecting a stream of acetylene molecules into the volume of reactantliquid to liberate a respective carbon ion in an excited state from atleast some of the acetylene molecules in the stream of acetylenemolecules; (d) collecting carbon nanostructures in the collection areaas carbon ions in the excited state traverse the surface of the volumeof reactant liquid and enter the collection area; and (e) removing thecarbon nanostructures from the collection area.
 2. The method of claim 1wherein the reactant liquid includes aluminum and maintaining thereactant liquid includes maintaining the aluminum at approximately 1650°F.
 3. The method of claim 1 further including providing one or morecollection surfaces in the collection area, and the step of collectingthe carbon nanostructures is performed on the one or more collectionsurfaces.
 4. The method of claim 3 wherein providing one or morecollection surfaces in the collection area includes retaining one ormore horizontally disposed plates in the collection area.
 5. The methodof claim 3 wherein providing one or more collection surfaces in thecollection area includes retaining one or more vertically disposedplates in the collection area.
 6. The method of claim 3 furtherincluding maintaining the one or more collection surfaces atapproximately 100° F. to 590° F.